Line coding is widely applied in the Ethernet system. Line coding is designed to enable the point-to-point system to use cost-effective optical receiver. Due to Direct Current (DC) balance and the small number of DC components of line coding, the line coding is more suitable for the Ethernet Passive Optical Network (EPON) system. Common line coding modes include: 9B10B line coding, 8B10B line coding, 64B/66B line coding, and 64B/65B line coding. The 8B10B coding efficiency is not high, and involves 20% redundancy. Neither the 64B/66B line coding nor the 64B/65B line coding solves the DC balance or ensures few DC components. Therefore, the 9B10B line coding is a relatively better coding manner.
In the current 9B10B line coding, each control character corresponds to a 9-bit source, and namely, there are 18 9-bit sources, where each 9-bit source corresponds to a 10-bit codeword and a 10-bit control character. For example, after “0 1010 1010” is encoded, the value “01 0101 0100” is a 10-bit codeword, and the value “01 0101 0101” is a control character. If the last bit is erroneous due to channel noise, the receiver is unable to decode the bits correctly, and the performance is deteriorated. Therefore, a new 9B10B line coding mode is required.